Are para-nitro-pyridine N-oxides quinonoid or benzenoid? An answer given by spatial NICS (TSNMRS)

The spatial magnetic properties (Through-Space NMR Shieldings-TSNMRS) of a number of substituted para-nitro-pyridine N-oxides have been computed, visualized as Iso-Chemical-Shielding-Surfaces (ICSS) of various size and direction, and were examined subject to the present quinonoid or benzenoid π-electron distribution of the six-membered ring.